Separation of oil and wax by continuous filtration



Sept- 30, 1952 w. KlERs-rED, JR., ETA. 2,612,465

SEPARATION OF' OIL AND WAX BY CONTINUOUS FILTRATION Filed June 29, 1948` El: MQSGNN m INVENTORS How /P H a 5 R J p m. W K P w W Y W mg QQ@ Nm Patented Sept. 30, 1.9-5.2

A UNITI-:D STATES PATENT-1 ff' l v 4 l y2,612,465` y' l y f s sEPAaA'rIoNoFlom AND WAX BY -1 CONTINUOUS 11L'rna'rioNY, y f l Wynkoop Kierstea, Jr., scarsdale, and Howard n H. Gross, Pleasantville, N. Y., assignors to ,-.1

Texaco Development Corporation, New York, m j N. Y., a corporation of Delaware 'Y y i r .l `Appnwtion June 29, 1948,1seria1 Naeasiasy v-6 Claims. (01.196-19) This invention relates to theseparation of oil and Waxby continuous filtration wherein. the oil-wax vmixture is filtered kin the presence of a solvent, liquid at, a temperature substantially belownormal atmospheric.

The invention. isi concerned-l. particularly with the,.-de waxing of wax-bearing lubricating oil stocks to `produce a vdevvaxed oil of low pour test and to obtain a wax product highly normal paraflinic in character. In accordance with the invention the filtration is effected in thepresence ofa relatively small proportion of added wax whichy is normal parafiinic in character.;HV

NkThe invention is Vparticularly advantageous from thestandpoint of obtaining a produtwax of low oil content and having amaterially -de creased content l of softwax or wax vwhich is highly isoparafiinicv in character.

y)The invention is tobe ydistinguishedfrom the devvaxing. operation disclosed.in U. yS.\Patent 2,248,498, granted toil-Inward H. Gross and Walter snuslofr. The patent-1n question. dislosesaef oyclingvlftothe filtering operationproduct was andi-preferablyda relatively low melting point portion ofthe product wax. The wax recircula-- tion orjthis patent has for its object the mareas-- ing of the ratio of wax tofoil inthe type of W'aXf bearingoil feed from which 'the wax is normally deposited in the foi-'m of a "cake which is -too dense for effective filter operation.

11n vthe practice of'fthe vpresent invention, the waxy product obtained from theprimary'lter operation is further treated to separate 'therefrom a fraction of relatively high meltingwpoint and which is highly normalparafilnic in charaoter. This highvmeltingvpoint fractiolnis recycled the primary yfiltering operation. It is advantageous to employ a staged filtering operation as illustrated in the accompanying drawy This drawing comprises a `diagram ,ot flow adapted to the treatment of a Wax-bearing 1ubricating oil distillate stock to obtain a dewaxed oil and also-albigh melting point wax rich in normal parafiinic constituents., 1

crystal structure. provision being :made forf-.ad-

dition of the solvent liquidzinsmall incrementsY at -succeeding stages of temperature reduction.

On the other hand, allof Athe solvent-mayibe' added prior to chilling Aif desired-.iuv The solvent liquid may'v be a, conventional dewaxing solventsuch as a-fmixturecom'prising about 45% methylethyl ketonefandi 55 com; mercial benzol and is conductedI from'aisource not shown'through',apipe` 3:.: In the eventzthat it is desiredr a portion vof? the solvent liquid vvmay v'volumeof oil.` This initial dilution may 'be'ef VReferring to the drawing, a Wax-bearing 11ibricating oil distillate derived from East Texas crude4 and having -a Saybolt Universal viscosity loi?V about /-60 seconds at 210 F. is conducted from tankage through a pipe I. toa-chillergZ `which latter is a conventional tubular type. n

Theinitial chilling of Vthe wax-bearing oil flowing through pipe I may be effectedr inthe substantial absence of solvent liquid if desired so ias togfacilitate the obtaining of the desired `the chiller at a temperature of :about `fect'ed by addition: of recycled filtrate as will tbe referred to later.

The Wax-bearing oilfvstream .partiallyi with solvent liquid,:o`r in the1-.`alternativ`e', in the substantial absence i of solvent', 5" flows; into.` the chiller 2. Afteripassage' through` a'fzportioniofj the chilling systemzcold solvent -liquidis diverted through pipe 6.- Iff'desired, anvr additionalifquan: tity of the solvent 'liquid may bezadded-yatz-:a succeeding point in the chiller;` Iasa-for.,example; through pipe 1. 2.-@

The wax-bearing oil and solvent liquid:leaves l5? F.; ;.At this point, it is mixed with. the'remainde the solvent separatelychilled to approxim this temperature, this further quantlitaotsol-g vent `being added through-f branch pipe.: 8".

vThe Wax-bearing mixture rdiluted;Wit' 3-4 volumes of-solvent liquid per volumeaof waabearing feed oil is then passed into a 'continuous rotaryfdrum `vacuum* filter l0 of: conventional vvill comprise a mixture i mal paraiinic constituents.

of isoparainic and nor- This slackv Wax is mixed with av quantity of i solvent liquid and drawn through branch pipe 20 and heat exchanger 2|. The mixture of solvent an'gg siaelzjwax passes 'tlnicniglif.l heat exe changer:v and s rought to"a ltemper'attire of about 30 Sufficient solvent is added to obsolvent per 1 volume of slack wax.. ,v

This mixture .is then passed tlr solvedin the main body of 'solvent liqui that the invention has application to the treat-rI ment of other stocks such as derived from Pennsylvania crudes.

In any case, it is contemplated eiecting the primary filtering operation in the presence of an added {WaxjWhicl/i consi'sj;sfjess'entiallytof;v normal para'fnsfa'nd which is-'SuHStantially *free from isoparaflins. By recirculating such Wax the oil f contentof the product Wax may be reduced by as The lter cake is dischargedgthrongh'pipe solvent liquid in the proportion of about l to 4 volumes zoiesolveritper, volume Vof Wax. A 'por'- of `:normali parafns.; The .recycled .wax 'passing lthroughgpipezliris injected into the wax-bearing oi'lr'feedstreai flowing through the pipe I..:Thev l' amoun'ts recycled ranges :from about 5L-20.%` 4by `i/olumeyof thfeedilchargep s branch pipe I lZI 'andinj ected into;v .the Waxbearl ing oil feedstream as indicated'is'lt may V.be 4injectedintmthisistream .priorto:introduction tov the chiller'f 2.1'or l 'aftepa'rtialchilling or); yif de-` siredfafter thifeedstream leavesthe chiller and prior.:tofintrocluctiol' togthei' filter.` I Y '1 to adjust the amount of filtraterecycleJsothat roportioiiso 'solid phase vand 'liquid lJohlld mixture undergoing '.,ltra-- l 23 Willwvary depending upon the melting point of i @i votierf ehvetioi" deiiraxng' 'solvent liquids `may, be employed. It is usually'preferred to eme ploy-a 'fritiireof alovv inolefciilirwight aliphatic l andfcompris'es high melting point Wax y,having a Y normal paraiinic character. It is also mixed with tion-whereof is;divertelthrbughpipe 2l While the Y y remainder isfdischargedfzand :the solventi recovmuch as 25 to 50% of that which is present in the productyvhenthe Wax recycling of this invention isnot'niloyed. Moreover, the product will be richer in normal Vpaf'afllns.

Y yNormal .paramnzwax hydrocarbons regardless ofnmole ular'wei'ght exhibit the same refractive indexvalu'e at their melting point namely 1.4365. *Iso parafiinic;y wax hydrocarbons have a much higherrefractive index value, Thus the slack Wax' removed from the filter l0 through pipe l5 when no Wax is being recycled may have a. refractiveindexi of about l1.4415 vto '1.4445f., On vthe other hand-When waxis beingiirecy'cled through pipe 21 .theewax ,product -removed from yiilte'r il Il will have afrefractive index of, about,l.4385l to:1.44`0.0.

Obviously many modifications-.and variations' of thefinventior'i as; above seta-forthlmay be made Without i departing-.1'fromU the spiriti andfflscope thereof; z and .therefore l' @only sucheilimitatios should be`.imposed' .asf are :indicated in tn'e ape Denddclaims.

1'.I In the separationofioilland Wax rm mix-` tures thereof; said wax. 'cmprisingjfbotnlndrmi and ijso'pa'rafnic' ednstituents, tnefimethdi c'inprisgfcontinuously 'passing stream orgs'id cui l kwax mixture with solvent liquides reducedteni'-v a primary yzone offlltfr'atiorieffctmgfsaid iiliirnaf eign ergs-eig mixtureb'f reduced temperatufefhereby' formingfileate'-feweeedwesp Siiuenis. end fecyclihee .bit

. sistingessentially of normal parains and havins,T a refractive index not in excess of about 1.4365, andl eiecting the ltration of theresulting mixture containing added wax at a temperature in the range about F. and below,

y thereby obtaining a lter cake the content of which has a refractive index in the range below about 1.4400.,l v

5. In the dewaxing of Wax-bearing lubricating oilv stock containing both normal and isoparaffin Wax constituents to 'produce dewaxed oil of 10W pour point and to obtain a Wax of highly filtration at a temperature in the range 0 F.

. and below thereby forming a filtrate of dewaxed oil and a lter cake of normal `and isoparain wax constituents, forming a uid mixture of said filter cake with solvent liquid, filtering said last .mentioned mixture at a temperature substantially above 0 F. and such" that a nitrate-connormal parafiinic character by chilling and continuous ltration of the resulting chilled mixture, the process which comprises eiecting said taining isoparain wax constituent is obtained v and a filter cake'consisting essentially of normal vparailin wax constituents is obtained, and recycling a small proportion of normal paraiiinv wax constituents` derived from said last mentioned lter lcake to the initial feed mixture prior to the rst mentioned filtration. 6. In the dewaxing of Wax-bearing-lubricating oil stock containing both normal and isoparan wax constituents to produce deWaXed oil of low pour point and to obtain a wax of highly normal parafnic character by a process involving chillingv and continuous filtration of a chilled mixtureof said wax-bearing oil and dewaxing solvent liquid to form a ltrate containingdewaxed oil and a lter cake of wax, the Wax content of said filter cakeas normally obtained be- -ing characterized by having a refractive index in the range about 1.4415 and higher, the improvement which comprises eiecting crystalli- Zation of substantially all of the normal and isoparafn Wax constituents in the presence of a small proportion of added Wax consisting essentially of normal parans and having a refractive index not in excess of about 1.4365, and effecting the filtration ofthe resulting mixture containing added Wax at a temperature in the range about 0 F. and below in a single filtering step and thereby obtaining a filter cake the Wax content of which has a refractive index in the range below about 1.4400. y

l WYNKOOP KIERSTE'), JR.

HOWARD I-I. GROSS.

REFERENCES CITED The following references` are of record in the le of this patent: 

1. IN THE SEPARATION OF OIL AND WAX FROM MIXTURES THEREOF, SAID WAX COMPRISING BOTH NORMAL AND ISOPARAFFINIC CONSTITUENTS, THE METHOD COMPRISING CONTINUOUSLY PASSING A STREAM OF SAID OILWAX MIXTURE WITH SOLVENT LIQUID AT REDUCED TEMPERATURE IN THE RANGE OF ABOUT 0* F. AND BELOW TO A PRIMARY ZONE OF FILTRATION, EFFECTING SAID FILTRATION OF SAID MIXTURE OF REDUCED TEMPERATURE THEREBY FORMING A FILTRATE OF DEWAXED OIL DISSOLVED IN SOLVENT LIQUID AND A WAX CAKE COMPRISING SAID WAX, DISCHARGING SAID FILTRATE, REMOVING SAID WAX CAKE, SUBJECTING SAID REMOVED WAX TO FILTRATION IN THE PRESENCE OF SOLVENT, LIQUID AT A TEMPERATURE 